>This is wrong, isn't it?

>This is in i386/pmap.c, pmap_changebit():
>
>			/*
>			 * XXX don't write protect pager mappings
>			 */
>			if ((PG_RO && setbits == PG_RO) ||
>			    (PG_RW && maskbits == ~PG_RW)) {
>				extern vm_offset_t pager_sva, pager_eva;
>
>				if (va >= pager_sva && va < pager_eva)
>					continue;
>			}

>Shouldn't the &&s in the first if be &?

it is ok.   note from pte.h:
#define PG_RO           0x00000000   /* read-only by user (and kernel if 486) */
#define PG_RW           0x00000002   /* read-write by user */

you have to be careful with PG_RO because it is zero (testing for
"setbits == 0" doesn't mean you are write protecting).

the compiler should reduce the if to:

  if (maskbits == ~PG_RW) {   /* do pager VA hack test... */ }

chuck